There has been an alarming increase in truck fires in recent years. Data suggest that the increased rate may be related to the newer emission standards for on highway diesel engines. In 2004 the Environmental Protection Agency (EPA) mandated lower levels of criteria emissions; nitrogen oxides (NOx) and particulate matter (PM). In 2007 there was another, more stringent, reduction in PM and the 2010 emission regulation will then further reduce the NOx emissions.
Both the 2004 and 2007 standards resulted in engine and exhaust after treatment technologies that create high heat rejection. Specifically, exhaust gas recirculation (EGR) technology was introduced and engine injection timing became more retarded. This results in a higher demand of the coolant system, higher under hood and in chassis temperatures. Starting in 2007 the lower PM standard was achieved on medium and heavy-duty vehicles by use of a diesel particulate filter (DPF) and in some cases a Diesel Oxidation Catalyst (DOC). These devices once activated can achieve temperatures above 1100° F. They are typically not under.
The hood but under or behind the cab. This has resulted in much higher in chassis temperatures as compared to earlier model vehicles. Typically the under hood temperatures and the under cab temperatures in the vicinity of the exhaust after treatment well exceed the flash point temperature of the #2 Diesel fuel which is 130° F. The elevated temperature can lead to degradation or compromising to components of the electrical systems.
The recent “Official Fleet Survey” conducted by The Technology and Maintenance Council (TMC) of the American Trucking Association (ATA) covered 130,000 in service tractors, 76,500 straight trucks and 300,000 trailers. The survey indicates Electrical, Fuel Systems and Engine failures are the cause of most fires with newer vehicle more receptive to fires than older vehicles.
The surveys and individual testimony suggest that electrical arcs or shorts are typically the cause of igniting diesel fuel or engine oil. These are referred to as electrical fires. It should be noted that an electric arc, high temperatures, fuel spill, or oil spill cannot in itself be a cause of a fire. It takes an arc or high temperature to ignite the flammable product. Some electrical fires involve material commonly used in vehicles other than fuel or oil.
The electrical fire incident associated with a severe accident is usually explained by movement of the drive train that will cause a chafing or tearing of the battery cables between the cables two fixed points, one on the frame rail and the other on an engine mount or starter assembly. Some drive trains are designed to allow the engine to dropdown in the event of an accident. This helps prevent the engine from penetrating through the fire wall. It also creates a high probability of the battery cables being ripped and torn open, along with fuel lines to the engine and the fuel crossover line between fuel tanks to rupture. There is no guarantee that the engine will stop running since the integrity of the alternator, engine wiring and engine ECU isn't jeopardized. Any fire caused by the accident can be further enabled by the engine pumping fuel, oil and/or air on to the fire. These types of fires are very intense and catastrophic. Roll over events are another cause of accident related electrical fires.
There is no vehicle manufacturer that currently offer a true automatic electrical disconnect in the event of an accident or abnormality in the electrical system. In fact, most modern diesel engines are designed so that the electrical power to the engine ECU remains on for several seconds after a key shut down so that electronic data can be properly stored in memory.
Earlier devices only disconnect the battery to ensure the engine cannot be started. None of these devices are structured to shut down the engine, once it is running, just by disconnecting the battery. This is because the alternator is a separate and primary source of electrical energy once the engine is running. The connection between the alternator and vehicle loads, including the engine electronics, ensure the engine continues to run. Furthermore none of these devices specifically addresses fire protection and detection.
This invention provides an automatic disconnect in the event of a crash, roll over, or abnormality in the electrical systems that create a high potential for fires. The invention will immediately cut electrical power from the batteries and ensures an immediate shutdown of the engine by removing all electrical power from the cab and engine. In addition there are temperature sensors and/or smoke detectors that are used to trigger an electrical disconnect. These features provide early detection and prevention, stemming from an electrical short or other events that can create elevated temperatures.